A transmission mechanism unit of an automatic transmission is constituted by including friction elements such as a brake, a clutch and the like. In order to prevent deterioration of durability of the friction element caused by overheat of the friction elements, supply of a lubricant flowrate according to heat generation amounts of the friction elements to the friction elements is important.
In the automatic transmission disclosed in JP10-141480A, a heat generation amount is calculated on the basis of a rotation speed difference between an input-side element and an output-side element of the friction element, and a lubricant flowrate according to the calculated heat generation amount is supplied to the friction element.